Magnetic core



April 19, 1949.

J. C. GRANFIELD MAGNETIC CORE 2 She ets-Sheet 1 Filed Jan. 9, 1947Inventzon John C. Granfield.

His AbEorney- April 1949- J. c. GRANFIELD MAGNETIC CORE 2 Sheets-Sheet 2Filed Jan. 9, 1947 Inventor.

John C. Granfield,

H is Atlc ofney.

Patented Apr. 19, 1949 UNITED STATES PATENT OFFICE MAGNETIC com:

John C. Granfield, Pittsfleld, Mass, assignor to General ElectricCompany, a corporation of New York Application January 9, 1947, SerialNo. 721,045

11 Claims.

This invention relates to magnetic cores and more particularly toimprovements in stacked cores of the split or divided lamination type.

By split or divided laminations is meant that the legs or yokes or bothin certain of the lamination layers consist of a plurality of parallelpunchings or lamination pieces. In other words, the total width of thesplit part of the layer is made up of two or more relatively narrowlamination pieces whose total width is equal to thequires very much moreforce to insert a wide yoke lamination thanit does to successivel inserttwo narrow laminations between the ends of the leg laniiriations. Afurther advantage is that it provides an improved flux path as comparedwith standard overlapping joints of solid cores in which the laminationsare not split without requiringthe additional cost and complexity ormitering the joints. This is particularly important when highly grainoriented magnetic mate rial is used. As the core is split, it is moredifficult for flux to travel across the grain or cross wise of the mostfavorable magnetic direction as the barrier produced by the splitprevents such cross migration of the flux. Consequently, the fluxtravels with the grain throughout a greater percentage of the meanlength turn of the core.

- Also, the narrower laminations reduce the eddy current losses in thecore.

The invention is characterized by having two of the lamination pieceswhich form one portion of a core layer make a joint with the samelamination piece which forms another portion of the same layer, in atleast alternate layers of the core. It is further characterized byhaving the butt joints between the laminations in each layer offset oroverlapped in contiguous layers so that there are no aligned butt jointsthroughout the thickness of the core.

Cores made in accordance with the invention have been found to havelower losses than equal size cores in which the laminations are unsplitThus large cores having relatively 2 and standard square cut overlappingjoints are used.

An object of the invention is to provide an improved split core forelectric induction apparatus.

Another object of the invention is to reduce the cost and losses oflarge size stacked cores made of magnetic strip material having a highlyfavorable magnetic direction parallel to the lengthwise dimension of thestrip.

The invention will be better understood from following description takenin connection" with the accompanying drawings and its scope will bepointed out in the appended claims.

In the drawings, Fig. l is a partially exploded perspective view of athree phase core having split legs and solid yokes and in which the adjacent layers are different; Fig. 2 is a similar ar tial view of a threephase core in which both the legs and yokes are split and in which allof the layers are the same; Fig. 3 is a modification of Fig. 2 in whichthe adjacent layers are differ ent; Fig. 4 is a similar view of a singlephase core having solid yokes and split legs in which all of the layersare the same; Fig. 5 is a similar view er a single phase core in whichboth the legs and yokes are split and the adjacent layers are different; Fig. 6 is a similar view of a three phase ccre in which both thelegs and yokes are split three ways and in which adjacent layers aredifferent;

.- Fig. 7 is a similar view of a single phase core in which both thelegs and yokes are split three ways and in which adjacent layers arediiierent, and

Fig. 8 is a modification of Fig. 5.

Referring now to the drawings and more partlcularly to Fig. '1, the coreis shown as comprising a plurality of superposed lamination layers inwhich the top layer I has been lifted off 'the stack to reveal thesecond layer 2. The third layer and all other odd numbered layers arethe same as layer l and the fourth layer and all other even numberedlayers are the same as layer 2. The layers are, of course, of the sameexternal outline or configuration and each defines two windows 3 and 4by means of three parallel legs 5, 6 and I and. two yokes 8 and 9 Thewidths of the correspondingly numbered legs and yokes in each layer arethe same and ordinarily the widths of all the legs will be the same andwill be equal to the widths of the yokes. In layer I and all oddnumbered layers, the outer legs 5 and I are each split into relativelylong narrow outer strip l0 and relatively short wide inner strip H. Themiddle leg 6 is split into a narrow strip [0 and a strip l2 which is ofthe same width as the strips .and all of the layers are the same. end ofthe top layer which has been shown lifted H but which is equal in lengthto strip HI. The yokes 8 and 8 each comprise duplicate strips l3 whichare the full width of the yokes. It will be.

observed with each outer corner that the two legged strips l and II eachmake butt contact with a yoke strip I3. In layer 2 and all the othereven numbered layers, the outer legs and I are split into long wideouter strips l2 and long narrow inner strips Hi. The middle leg is splitinto a wide left hand strip II and narrow right hand strip [4 which isthe same width as the strips l0 and the same length as the strips II.The yokes 8 and 9 consist of'one piece strips l5 which are the samewidth as the yoke pieces l3 but which run from the inside of one outerleg to the width of the other outer leg.

It will be observed that none of the butt joints in layers l and 2 willcoincide with each other when the layers are superposed. It will also beobserved that due to the reversal of the widths of the strips in thelegs of adjacent layers, the split in the legs is also overlapped oroffset in adjacent layers.

It will be observed that in layer 2, the outer leg strips l2 do not makebutt contact with the yoke strips l5. This could readily be accomplishedby cutting off the inner leg strips [0 along the dotted lines andextending the ends of the yoke strips G5 to make contact with the outerleg strips [2. However, if that were done, then the butt joints formedat the dotted lines between the ends of the shortened inner leg stripsill and the yoke strips i5 would be in registration' with the innerportion of the butt joints between the yoke strips l3 and the inner wideleg strips ii in layer I so that, in effect, there would be a partialbutt joint throughout the entire thickness of the core.

As has been explained above, the benefits derived from splitting thecore increase with the ,size of the core and the width of the leg andyoke portions of the lamination layers. Consequently the core shown inFig. 1 may either be considered as a single width core or else it may beconsidered as the wide central portion of a so- ;called stepped orcruciform cross section core in which groups of progressively narrowerwidth -laminations are placed on both sides of the wide stack shown inthe drawing so as to form the steps.

The offsetting or overlapping of the steps in .the legs tends to holdthe core tightly together and prevent the looseness which might occur ifthe widths of the two parts of the legs were not reversed in adjacentlayers.

In Fig. 2, both the legs and the yokes are split Thus, the

off the stack is the same as the opposite end (not shown) of the secondlayer which is on the top of the stack. In other words, every otherlayer is rotated 180 about a central axis perpendicular to the plane ofthe lamination layer. The left hand leg of the lifted off layer of oddnumbered layers is split into a wide strip I6 and a narrow strip I1 andrespective duplicates of these strips form the right hand leg of thesecond and all even numbredlayers. Likewise, the right hand leg of thetop and all odd numbered layers and the left hand leg of the second andall even numbered layers are made from wide strips l8 and narrow stripsl9 which preferably correspond respectively in width to the strips l6and. H. The center legs are made of wide full length strips l8 .andnarrow short length strips which have the same width as the strips l6and 20. Strips 20 are preferably the same width as the strips l1 and I9.The right hand and left hand parts of the yokes are different from eachother at each end and the two ends are also different from each other sothat the layers are not symmetrical. The end of the top lifted off layerand all odd numbered layers which is shown, corresponds with the-lefthand end of the second and all even numbered layers, which are notshown, and it is characterized by having wide punchings 2i and 22 on theoutside and narrow punchings 23 and 24 on the inside, punchings 2| and23 being adjacent each other and being of different lengths and thepunchings 22 and 24 being adjacent each other and being of the samelength. Opposite ends of the layers, one of which is shown in the secondlayer has narrow punchings 25 and 28 on the outside and has widepunchings 22 and 21 on the inside. It will be observed that the samesize punching 22 is used at both ends of each layer. The lengths of theadjacent wide and narrow punchings, which are shown in the second layer,are difierent for each pair.

It will be observed in Fig. 2 that at each corner of each layer eitherone leg punching makes contact with at least two yoke punchings or elseone yoke punching makes contact with at least two leg punchings. Thus,at the right hand corner of the lifted on layer the long strip orpunching i9 makes contact with both punchings 22 and 24 while at theopposite corner of the same layer, leg strip ll makes contact with bothyoke punchings 2i and 23. Also, in the right hand corner the yokepunching 2d makes contact with both leg punchings i8 and i9 and in theopposite corner the yoke punching 25 makes contact with both legpunchings l6 and ii. Similar relationships exist at the other end of thelayers as shown in the illustrated and of the second layer.

In the modification shown in Fig. 3, the adjacent layers are differentfrom each other in internal configuration. That is to say, all the oddnumbered layers are of one kind and all the even numbered layers are ofanother kind. Thus, the odd numbered layers starting with the lifted offlayer l have narrow strips as on the outside of both the outer legs andhave wide strips 29 on .the inside of those legs whereas the evennumbered layers have wide strips 39 on the outside of the outer legs andnarrow strips 3! on the inside of the outer legs. The ends of thelayers, which are not shown, are identical respectively with the ends ofthose layers which are shown. Thus, the opposite end of the lifted offlayer is the same as the end which is shown and the same is true for thesecond layer. The odd numbered layers have wide strips 32 on the rightin the center leg which strips are not quite as long as the core. Theeven numbered layers have wide strips 33 on the left which are the fulllength of the core. Both center legs have narrow strips 343 of the sameshape except that they are on the left in the odd numbered layers and onthe right in the even numbered layers, as the core is viewed in thedrawing. The inside to outside relationship of the widths of theportions of the yokes in each layer correspond to the same relationshipfor the outer legs of those layers. Thus, in the odd numbered layers,narrow strips 35 and 36 are on the outside and wide strips 31 and 38 areon they inside whereas in the even numbered layers, wide strips 39 andas are on the outside and narrow strips 4i and 42 are on the inside- Asin the other figures, the corners of the layers and the core arecharacterized by multiple contact between one punching or laminationstrip and one portion of the core and a plurality of punchings orlamination strips in another portion of the core and the butt Joints donot register in contiguous layers and are overlapped in all such layers.

Fig. 4 is similar to Fig. 1 in that the legs only are split and theyokes are unsplit but this is a single phase core and in addition itdiffers from Fig. 1 in that the layers are all the same. Furthermore,these layers are symmetrical about a lateral axis or center line. Oneleg of each layer consists of a full length narrow strip 43 on theoutside and a full length wide strip 44 on the inside. The other legconsists of another full length wide strip 44 on the outside and anarrow short strip 45 on the inside. The yokes consist of identicalpunchings 46 which have a width equal to the combined width of the wideand narrow leg punchings. The layers are not symmetrical about theirlongitudinal center line or axis, and successive layers are rotated 180about such axis or about an axis perpendicular to the plane of thelaminations so as to provide overlapping of all joints. It will be seenthat at each corner at least one layer of each pair of contiguous layershas a yoke punching which makes contact with both leg punchings becauseyoke punching 46 makes contact with both leg punchings 44 and 45 and asthe laminations are successively reversed, this relationship' will occurin each pair of contiguous layers at each corner. g

In Fig. 5, there is a single phase core in which both the legs and yokesare split. In this core, theodd numbered layers are all of one kind andthe even numbered layers are all of another kind.

-The legsof the top and all odd numbered layers,

may be made of duplicate wide full length outer punchings 4d, one ofwhich is associated with a short length narrow punching and the other ofwhich is associated with an intermediate length narrow punching ii. Theyoke consists of a wide inner punching 48 and a narrow outer punching49. The opposite end of the top layer has not been shown but isthe sameas the endwhich has been shown. In the even numbered layers, the legscomprise full length narrow outer strips 43 A with one of which isassociated a short length inner wide strip and the other of which isassociated with a medium length wide strip 5 i. The yoke of these layershas a wide outer strip 52 and narrow innerstrip '53. Opposite ends ofthe even numbered layers are the same as the end which has been shown. a

The core of Fig. l5,"like the other figures, is characterized bycomplete overlapping of all butt joints and multiple contact between theends of punchings of the leg and yoke portions. Thus, in the top liftedofi layer both leg strips 44 and 41 make contact with the same yokestrip 49 and the yoke strip 48 makes contact with both leg strips 44 and45. In the even numbered layers corresponding relationships exist.

In Fig. 6, there is a three way rather than a two way split three phasecore in which both the yokes andthe legs are split into three parallelstrips or punchings in each layer. The odd numbered layers are all ofone kind and the even numbered layers are all of a different kind. Thetwo opposite ends of any one layer are the same so that only one end ofeach of the two kinds of layers has been shown. The narrowest strips,which all may be of the same width, are desi nated by the same referencenumber 54 in all of the legs and yokes. Although, of course, it will beobvious from the drawing that these narrowest length strips are ofvarying lengths but in view of the descriptions of the previous figures,it is believed the details regarding the differences in lengths of thevarious pieces will be obvious from the drawing so that it isunnecessary to assign a different number to each different length pieceof the same width. The intermediate width strips or punchings in all ofthe portions of the core are designated by the numeral 55. Likewise, thewidest strips in all the portions'of the core are designated by thenumeral 56.

' Fig. 6 is characterized by the same complete overlappin of the buttjoints in contiguous layers and the multiple contacts of strips orpunchings at the corners.

Fig. '7 is a single'phase core which is essentially the same as Fig. 6except that the middle leg has been omitted and the yoke punchingsextend con tinuously between the two outer legs. The different widthpunchings or strips are designated as in Fig. 6.

In the modification of Fig. 5 shown in Fig. 8, the opposite ends of thesame lamination layer are different instead of being the same so that acomplete odd numbered layer has been shown lifted off to reveal acomplete even numbered layer beneath it. correspondingly numbered parts51, 58, 59 and are respectively the same in all layers and theseconstitute what may be called the outer zone of each layer, there beingtwo narrow parts 51 and 58 forming one corner andtwo wide parts 59 and60 forminga diagonally-opposite corner. f

In the odd numbered layers,..the inner. zone comprises two wide stripsSi and 52'and two narrow strips 63 and .54 while in the even numberedlayers, the'inner zone comprises two wide strips 65 and 66 which aredifferent in length respectively- The inner 1 length of'members 62 and68 is the san e. Like-' wise, the length of the members iii and El isthesame and the length of members 63 and 65 is-the same.

The superposition layers causes complete overlapping of all the buttjoints in the layers and as will be seen in each layer there is multiplecontact at the corners between various lamination pieces of differentportions of the core.

While there have been shown and described particular embodiments of theinvention, it will be obvious to those skilled in the art that changesand modifications can be made without departing from the invention andtherefore it is aimed in the appended claims to cover all such changesand modifications as fall within the true spirit and scope of theinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A core including superposed fiat lamination layers each having atleast two leg and two yoke portions, the leg portions being splitlongitudinally into at least two different width pieces of magneticstrip material, the yoke portions comprising at least one piece ofmagnetic strip material, the lengths of said pieces in one of every pairof contiguous leg layers being different, said different length piecesbeing in contact with the same yoke piece.

However, it.will be observed that the lengthof the outer even numbered2. A core including superposed flat lamination layers each having atleast two leg and two yoke portions, the leg portions being splitlongitudinally into at least two different width pieces of magneticstrip material, the yoke portions comprising at least one piece ofmagnetic strip material, the lengths of said pieces in one of every pairof contiguous leg portions being different, said different length piecesbeing in contact with the same yoke piece, one set of alternate layersbeing similar to each other and different from the remaining set ofalternate layers which in turn are similar to each other.

3. A core including superposed 'fiat lamination layers each having atleast two leg and two yoke portions, the leg portions being splitlongitudinally into at least two different width pieces of magneticstrip material, the yoke portions comprising at least one piece ofmagnetic strip material, the lengths of said pieces in one of every pairof con tiguous leg portions being different, said different lengthpieces being in contact with the same yoke piece, all of said layersbeing identical in structure, one alternate set of layers being reversedin" position relative to the remaining set of intermediate layers.

4. A core including superposed flat lamination layers each having atleast two leg and two yoke portions, the leg portions being splitlongitudinally into at least two different width pieces of magneticstrip material, the yoke portions each comprising full width pieces ofmagnetic strip material, the lengths of said pieces in one of every pairof contiguous leg portions being different, said different length legpieces being in contact with the same yoke pieces.

5. A core including superposed fiat lamination layers each having atleast two leg and two yoke portions each forming four corners by meansof butt joints, the leg portions being longitudinally split intoparallel strips, the yoke portions being strips of the full width of theyokes, at each corner one alternate set of layers having the leg stripsextend out to the edge of the layer with the end of the yoke strip incontact with the inner leg strip only and in the remaining layers theouter leg strip only extending out to the edge of the layer with the endof the with both of the leg strips.

6. A three phase core including superposed lamination layers each havingthree split legs and two unsplit yokes, the three legs being in the sameplaneand parallel to each other whereby there are two outer legs and aninner leg, each outer leg comprising an outer strip and an inner strip,the even numbered layers starting at a given layer in the core havingfull length outer legs between which the yokes extend with a shorterinner leg which extends between the yokes, the odd numbered layershaving a full lengthcenter leg from both ends of which the yokes extendlaterally in opposite directions with full length outer strips on theouter legs between which the yokes extend and With'shorter inner stripson the outer legs which extend between the yokes.

7. A core including superposed fiat lamination layers each having atleast two leg and two yoke yoke strip in contact portions, the legportions and the yoke portions being split longitudinally into at leasttwo different width pieces of magnetic strip material, the

length of said pieces in one of every pair of contiguous leg portionsbeing different, said diflerent length leg pieces being in contact withthe same yoke piece, the lengths of said pieces in one of every pair ofcontiguous yoke portions being different, said different length yokepieces being in contact with the same leg piece.

8. A core including superposed flat lamination layers each having atleast two leg and two yoke portions, the leg and yoke portions beingsplit longitudinally into three different width pieces of magnetic stripmaterial, the widest piece being between the other two pieces in all thelegs and yokes, said widest pieces in each leg and yoke beingintermediate in length to the pieces on both sides thereof, thenarrowest pieces being on the outside of the legs and on the inside ofthe yokes in one set of alternate layers and the narrowest pieces beingon the inside of the legs and on the outside of the yokes in theremaining set of alternate layers.

9. A three phase core including superposed fiat lamination layers eachhaving three legs and two yokes, the legs and yokes being splitlongitudinally into three diiferent width pieces of magnetic stripmaterial, the widest strips being between the other strips in all of thelegs and yokes, the narrowest strips being on the outside of the outerlegs and on the inside of the yokes in one set of alternate layers, thenarrowest strips being on the inside of the outer legs and on theoutside of the yokes in the other set of alternate layers, the relativepositions of the narrowest strips being reversed in the center legs ofsuccessive layers.

10. A core including superposed flat lamination layers each having atleast two leg and two yoke portions, the leg portions and the yokeportions being split longitudinally into at least two difierent widthpieces of magnetic strip material, the lengths of the difierent widthpieces in each leg and yoke portion being difierent, the ends of saidpieces fitting snugly together in square butt joints.

11. A core including similar superposed flat lamination layers eachhaving at least two leg and two yoke portions, the leg portions and theyoke portions being split longitudinally into at least two differentwidth pieces of magnetic strip material, the lengths of the differentwidth pieces in each leg and yoke portion being different, the ends ofsaid pieces in adjacent portions of each layer fitting snugly togetherin square butt joints, said layers having four difierent corners one ofwhich has the widest pieces on the inside and the narrowest pieces onthe outside, the diagonally opposite corner having the narrowest pieceson the inside and the widest pieces on the outside, the third cornerhaving one wide piece and one narrow piece on the outside and one widepiece and one narrow piece on the inside, the last corner having thesame width relationship but having the relative lengths of the differentwidth pieces reversed, alternate layers being reversed.

JOHN C. GRANFIELD.

REFERENCES CITED The following references are file of this patent:

UNITED STATES PATENTS of record in the

